Methods of making metal bond abrasive articles and metal bond abrasive articles

ABSTRACT

Methods of making metal bond abrasive articles via powder bed jetting are disclosed. Metal bond abrasive articles prepared by the method include abrasive articles having arcuate or tortuous cooling channels, abrasive segments, abrasive wheels, and rotary dental tools.

TECHNICAL FIELD

The present disclosure broadly relates to methods of making abrasivearticles having abrasive particles in a metallic bonding matrix.

BACKGROUND

Traditionally, metal bond abrasive articles are made by mixing anabrasive grit, such as diamond, aluminum oxide, cubic boron nitride(cBN), or other abrasive grains with a non-melting metal powder (e.g.,tungsten, stainless steel, or others), a melting metal powder (e.g.,bronze or copper), or a combination thereof. Pore inducers, temporarybinders and other additives may be added. The mixture is then introducedinto a mold that has been coated with a mold release agent. The filledmold is then compressed in a press to form a molded green body. Thegreen body then is ejected from the mold and subsequently heated in afurnace at high temperature to melt a portion of the metal composition,or it is infused with a molten metal. The heating is typically done in asuitable controlled atmosphere of inert or reducing gas (e.g., nitrogen,argon, hydrogen) or vacuum.

There are many disadvantages to this manufacturing approach: eachabrasive article shape requires a specialized mold; the molds typicallyare expensive and have a long lead time to make; any design changerequires the manufacture of a new mold; there are limitations to theshapes that can be molded, complicated shapes with undercuts or internalstructures such as cooling channels are generally not possible; moldswear out and have a limited number of units that can be manufactured permold; while the molds are filled with the abrasive mixture, separationof the components can occur, leading to inhomogeneous abrasivecomponents and density variation, which is easily visible; and theprocess is manual and labor intensive.

Powder bed binder jetting is an additive manufacturing, or “3D printing”technology, in which a thin layer of a powder is temporarily bonded atdesired locations by a jetted liquid binder mixture. Typically, thatbinder mixture is dispensed by an inkjet printing head, and consists ofa polymer dissolved in a suitable solvent or carrier solution. In onemethod, the binder is a powder which is mixed with the other powder, orcoated onto the powder and dried, and then an activating liquid, such aswater or a solvent mixture, is jetted onto the powder, activating thebinder in select areas.

The printed powder layer is then at least partially dried and lowered sothat a next powder layer can be spread. The powder spreading, bondingand drying processes can be repeated until the full object is created.The object and surrounding powder is removed from the printer and oftendried or cured to impart additional strength so that the now hardenedobject can be extracted from the surrounding powder.

SUMMARY

In a first aspect, the present disclosure provides a method of making ametal bond abrasive article, the method comprising the sequential steps:

-   -   a) a subprocess comprising sequentially:        -   i) depositing a layer of loose powder particles in a            confined region, wherein the loose powder particles comprise            higher melting metal particles and abrasive particles, and            wherein the layer of loose powder particles has            substantially uniform thickness;        -   ii) jetting a liquid binder precursor material onto at least            one predetermined region of the layer of loose powder            particles;        -   iii) converting the liquid binder precursor material into a            binder material that bonds together the loose powder            particles in the at least one predetermined region to form a            layer of bonded powder particles;    -   b) independently carrying out step a) a plurality of times to        generate an abrasive article preform comprising the bonded        powder particles and remaining loose powder particles, wherein        the abrasive article preform has a predetermined shape, and        wherein in each step a), the loose powder particles are        independently selected, and the liquid binder precursor material        is independently selected;    -   c) separating substantially all of the remaining loose powder        particles from the abrasive article preform;    -   d) infusing the abrasive article preform with a molten lower        melting metal, wherein at least some of the higher melting metal        particles do not completely melt when contacted by the molten        lower melting metal; and    -   e) solidifying the molten lower melting metal to provide the        metal bond abrasive article.

In yet another aspect, the present disclosure provides a method ofmaking a metal bond abrasive article, the method comprising sequentialsteps:

-   -   a) a subprocess comprising sequentially:        -   i) depositing a layer of loose powder particles in a            confined region, wherein the loose powder particles comprise            metal particles and abrasive particles, and wherein the            layer of loose powder particles has substantially uniform            thickness;        -   ii) jetting a liquid binder precursor material onto at least            one predetermined region of the layer of loose powder            particles;        -   iii) converting the liquid binder precursor material into a            binder material that bonds together the loose powder            particles in the at least one predetermined region to form            bonded powder particles;    -   b) independently carrying out step a) a plurality of times to        generate an abrasive article preform comprising the bonded        powder particles and remaining loose powder particles, wherein        the abrasive article preform has a predetermined shape, and        wherein in each step a), the loose powder particles are        independently selected, and the liquid binder precursor material        is independently selected;    -   c) separating substantially all of the remaining loose powder        particles from the abrasive article preform; and    -   d) heating the abrasive article preform to provide the metal        bond abrasive article.

Advantageously, methods according to the present disclosure are suitablefor making metal bond abrasive articles, either in large volume or shortrun production.

Accordingly, in another aspect, the present disclosure provides a metalbond abrasive article comprising a metallic binder material havingabrasive particles retained therein, wherein the metal bond abrasivearticle has at least one tortuous cooling channel extending at leastpartially therethrough.

In yet another aspect, the present disclosure provides a metal bondabrasive article comprising a metallic binder material having abrasiveparticles retained therein, wherein the metal bond abrasive article hasat least one arcuate cooling channel extending at least partiallytherethrough.

In yet another aspect, the present disclosure provides a metal bondabrasive article precursor comprising metallic particles and abrasiveparticles bonded together by a binder precursor material, wherein themetal bond abrasive article precursor further comprises at least one of:

-   -   at least one tortuous cooling channel extending at least        partially through the metal bond abrasive article precursor; or    -   at least one arcuate cooling channel extending at least        partially through the metal bond abrasive article precursor.

In yet another aspect, the present disclosure provides a rotary dentaltool, wherein at least a portion of the dental tool comprises abrasiveparticles dispersed and retained in a porous metal bond matrixcomprising sintered metal particles.

Features and advantages of the present disclosure will be furtherunderstood upon consideration of the detailed description as well as theappended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic process flow diagram of a method of making a metalbond abrasive article according to the present disclosure.

FIG. 2 is a schematic perspective view of an exemplary dental bur 200preparable according a method of the present disclosure.

FIG. 3 is a schematic cross-sectional top view of an exemplary metalbond abrasive wheel 300 preparable according to the present disclosure.

FIG. 4 is a schematic cross-sectional top view of an exemplary metalbond abrasive wheel 400 preparable according to the present disclosure.

FIG. 5 is a schematic perspective view of an exemplary metal bondabrasive segment 500.

FIG. 6 is a schematic perspective view of an exemplary metal bondabrasive wheel 600.

Repeated use of reference characters in the specification and drawingsis intended to represent the same or analogous features or elements ofthe disclosure. It should be understood that numerous othermodifications and embodiments can be devised by those skilled in theart, which fall within the scope and spirit of the principles of thedisclosure. The figures may not be drawn to scale.

DETAILED DESCRIPTION

Methods of making a metal bond abrasive articles according to thepresent disclosure include a common additive subprocess. The subprocesscomprises sequentially, preferably consecutively (although not required)carrying out at least three steps.

FIG. 1 schematically depicts an exemplary powder bed jetting process 100used in making a metal bond abrasive article.

In the first step, a layer 138 of loose powder particles 110 from powderchamber 120 a with movable piston 122 a is deposited in a confinedregion 140 in powder chamber 120 b with movable piston 122 b. The layer138 should be of substantially uniform thickness. For example, thethickness of the layer may vary less than 50 microns, preferably lessthan 30 microns, and more preferably less than 10 microns. The layersmay have any thickness up to about 1 millimeter, as long as the jettedliquid binder precursor material can bind all the loose powder where itis applied. Preferably, the thickness of the layer is from about 10microns to about 500 microns, more preferably about 10 microns to about250 microns, more preferably about 50 microns to about 250 microns, andmore preferably from about 100 microns to about 200 microns.

The loose powder particles comprise higher melting metal particles andabrasive particles.

The higher melting metal particles may comprise any metal from group 2through to group 15 of the Periodic Table of the elements, for example.Alloys of these metals, and optionally with one or more elements (e.g.,metals and/or non-metals such as carbon, silicon, boron) in groups 1 and15 of the Periodic Table, may also be used. Examples of suitable metalparticles include powders comprising magnesium, aluminum, iron,titanium, niobium, tungsten, chromium, tantalum, cobalt, nickel,vanadium, zirconium, molybdenum, palladium, platinum, copper, silver,gold, cadmium, tin, indium, tantalum, zinc, alloys of any of theforegoing, and combinations thereof.

The higher melting metal particles preferably having a melting point ofat least about 1100° C., and more preferably at least 1200° C., althoughlower melting metals may also be used. Examples include stainless steel(about 1360-1450° C.), nickel (1452° C.), steel (1371° C.), tungsten(3400° C.), chromium (1615° C.), Inconel (Ni+Cr+Fe, 1390-1425° C.), iron(1530° C.), manganese (1245-1260° C.), cobalt (1132° C.), molybdenum(2625° C.), Monel (Ni+Cu, 1300-1350° C.), niobium (2470° C.), titanium(1670° C.), vanadium (1900° C.), antimony (1167° C.), Nichrome (Ni+Cr,1400° C.), alloys of the foregoing (optionally also including one ormore of carbon, silicon, and boron), and combinations thereof.Combinations of two or more different higher melting metal particles mayalso be used.

The abrasive particles may comprise any abrasive particle used in theabrasives industry. Preferably, the abrasive particles have a Mohshardness of at least 4, preferably at least 5, more preferably at least6, more preferably at least 7, more preferably at least 8, morepreferably at least 8.5, and more preferably at least 9. In certainembodiments, the abrasive particles comprise superabrasive particles. Asused herein, the term “superabrasive” refers to any abrasive particlehaving a hardness greater than or equal to that of silicon carbide(e.g., silicon carbide, boron carbide, cubic boron nitride, anddiamond).

Specific examples of suitable abrasive materials include aluminum oxide(e.g., alpha alumina) materials (e.g., fused, heat-treated, ceramic,and/or sintered aluminum oxide materials), silicon carbide, titaniumdiboride, titanium nitride, boron carbide, tungsten carbide, titaniumcarbide, aluminum nitride, diamond, cubic boron nitride, garnet, fusedalumina-zirconia, sol-gel derived abrasive particles, cerium oxide,zirconium oxide, titanium oxide, and combinations thereof. Examples ofsol-gel derived abrasive particles can be found in U.S. Pat. No.4,314,827 (Leitheiser et al.); U.S. Pat. No. 4,623,364 (Cottringer etal.); U.S. Pat. No. 4,744,802 (Schwabel); U.S. Pat. No. 4,770,671(Monroe et al.); and U.S. Pat. No. 4,881,951 (Monroe et al.).Agglomerate abrasive particles that comprise finer abrasive particles ina vitreous bond matrix (e.g., as described in U.S. Pat. No. 6,551,366(D'Souza et al.)) may also be used.

The abrasive particles may be coated with a metal to facilitate bondingwith other metallic components (higher and/or lower melting metalparticles and/or infused metal) of the abrasive article; for example, asdescribed in U.S. Pat. Appl. Publ. No. 2008/0187769 A1 (Huzinec) or U.S.Pat. No. 2,367,404 (Kott).

In order to achieve fine resolution, the loose powder particles arepreferably sized (e.g., by screening) to have a maximum size of lessthan or equal to 400 microns, preferably less than or equal to 250microns, more preferably less than or equal to 200 microns, morepreferably less than or equal to 150 microns, less than or equal to 100microns, or even less than or equal to 80 microns, although larger sizesmay also be used. The higher melting metal particles, abrasiveparticles, optional lower melting metal particles, and any optionaladditional particulate components may have the same or different maximumparticle sizes, D₉₀, D₅₀, and/or D₁₀ particle size distributionparameters.

The loose powder particles may optionally further comprise lower meltingmetal particles (e.g., braze particles). The lower melting metalparticles preferably have a maximum melting point that is at least 50°C. lower (preferably at least 75° C. lower, at least 100° C., or even atleast 150° C. lower) than the lowest melting point of the higher meltingmetal particles. As used herein, the term “melting point” includes alltemperatures in a melting temperature range of a material. Examples ofsuitable lower melting metal particles include particles of metals suchas aluminum (660° C.), indium (157° C.), brass (905-1083° C.), bronze(798-1083° C.), silver (961° C.), copper (1083° C.), gold (1064° C.),lead (327° C.), magnesium (671° C.), nickel (1452° C., if used inconjunction with higher melting point metals), zinc (419° C.), tin (232°C.), active metal brazes (e.g., InCuAg, TiCuAg, CuAg), alloys of theforegoing, and combinations thereof.

Typically, the weight ratio of high melting metal particles and/oroptional lower melting metal particles to the abrasive particles rangesfrom about 10:90 to about 90:10, although this is not a requirement.

The loose powder particles may optionally further comprise othercomponents such as, for example, pore inducers, fillers, and/or fluxingagent particles. Examples of pore inducers include glass bubbles andorganic particles. In some embodiments, the lower melting metalparticles may also serve as a fluxing agent; for example as described inU.S. Pat. No. 6,858,050 (Palmgren).

The loose powder particles may optionally be modified to improve theirflowability and the uniformity of the layer spread. Methods of improvingthe powders include agglomeration, spray drying, gas or wateratomization, flame forming, granulation, milling, and sieving.Additionally, flow agents such as, for example, fumed silica,nanosilica, stearates, and starch may optionally be added.

Next, a liquid binder precursor material 170 is jetted by printer 150onto predetermined region(s) 180 of layer 138. The liquid binderprecursor material thus coats the loose powder particles in region 180,and is subsequently converted to a binder material that binds the loosepowder particles in region 180 to each other. The liquid binderprecursor material may be any composition that can be converted (e.g.,by evaporation, or thermal, chemical, and/or radiation curing (e.g.,using UV or visible light)) into a binder material that bonds the loosepowder particles together according to the jetted pattern (and ultimate3-D shape upon multiple repetitions).

In some embodiments, the liquid binder precursor material comprises aliquid vehicle having a polymer dissolved therein. The liquid mayinclude one or more of organic solvent and water. Exemplary organicsolvents include alcohols (e.g., butanol, ethylene glycol monomethylether), ketones, and ethers, preferably having a flash point above 100°C.

Selection of a suitable solvent or solvents will typically depend uponrequirements of the specific application, such as desired surfacetension and viscosity, the selected particulate solid, for example.

The liquid vehicle can be entirely water, or can contain water incombination with one or more organic solvents. Preferably, the aqueousvehicle contains, on a total weight basis, at least 20 percent water, atleast 30 percent water, at least 40 percent water, at least 50 percentwater, or even at least 75 percent water.

In some embodiments, one or more organic solvents may be included in theliquid vehicle, for instance, to control drying speed of the liquidvehicle, to control surface tension of the liquid vehicle, to allowdissolution of an ingredient (e.g., of a surfactant), or, as a minorcomponent of any of the ingredients; e.g., an organic co-solvent may bepresent in a surfactant added as an ingredient to the liquid vehicle.Exemplary organic solvents include: alcohols such as methyl alcohol,ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,sec-butyl alcohol, t-butyl alcohol, and isobutyl alcohol; ketones orketoalcohols such as acetone, methyl ethyl ketone, and diacetonealcohol; esters such as ethyl acetate and ethyl lactate; polyhydricalcohols such as ethylene glycol, diethylene glycol, triethylene glycol,propylene glycol, butylene glycol, 1,4-butanediol, 1,2,4-butanetriol,1,5-pentanediol, 1,2,6-hexanetriol, hexylene glycol, glycerol, glycerolethoxylate, trimethylolpropane ethoxylate; lower alkyl ethers such asethylene glycol methyl or ethyl ether, diethylene glycol ethyl ether,triethylene glycol methyl or ethyl ether, ethylene glycol n-butyl ether,diethylene glycol n-butyl ether, diethylene glycol methyl ether,ethylene glycol phenyl ether, propylene glycol methyl ether, dipropyleneglycol methyl ether, tripropylene glycol methyl ether, propylene glycolmethyl ether acetate, dipropylene glycol methyl ether acetate, propyleneglycol n-propyl ether, dipropylene glycol n-propyl ether, tripropyleneglycol n-propyl ether, propylene glycol n-butyl ether, dipropyleneglycol n-butyl ether, tripropylene glycol n-butyl ether, propyleneglycol phenyl ether, and dipropylene glycol dimethyl ether;nitrogen-containing compounds such as 2-pyrrolidinone andN-methyl-2-pyrrolidinone; sulfur-containing compounds such as dimethylsulfoxide, tetramethylene sulfone, and thioglycol; and combinations ofany of the foregoing.

The amounts of organic solvent and/or water within the liquid vehiclecan depend on a number of factors, such as the particularly desiredproperties of the liquid binder precursor material such as theviscosity, surface tension, and/or drying rate, which can in turn dependon factors such as the type of ink jet printing technology intended tobe used with the liquid vehicle ink, such as piezo-type or thermal-typeprintheads, for example.

The liquid binder precursor material may include a polymer that issoluble or dispersible in the liquid vehicle. Examples of suitablepolymers may include polyvinyl pyrrolidones, polyvinyl caprolactams,polyvinyl alcohols, polyacrylamides, poly(2-ethyl-2-oxazoline) (PEOX),polyvinyl butyrate, copolymers of methyl vinyl ether and maleicanhydride, certain copolymers of acrylic acid and/or hydroxyethylacrylate, methyl cellulose, natural polymers (e.g., dextrin, guar gum,xanthan gum). Of these, polyvinyl pyrrolidones are preferred for usewith liquid vehicles that are predominantly water. Other organicpolymers than those listed above may be used instead or in addition ifdesired.

The liquid binder precursor material may include one or morefree-radically polymerizable or otherwise radiation-curable materials;for example, acrylic monomers and/or oligomers and/or epoxy resins. Aneffective amount of photoinitiator and/or photocatalysts for curing thefree-radically polymerizable or otherwise radiation-curable materialsmay also be included. Examples of suitable (meth)acrylate monomers andoligomers and otherwise radiation-curable materials (e.g., epoxy resins)can be found in, for example, U.S. Pat. No. 5,766,277 (DeVoe et al.).

In some preferred embodiments, the liquid binder precursor material isessentially free of (e.g., contains less than 1 percent, less than 0.1percent, less than 0.01 percent, or is even free of) inorganiccomponents (other than water) that would not be volatilized duringsintering of the higher and/or lower melting metal particles. The liquidbinder precursor material may be free of metal nanoparticles and/ormetal oxide nanoparticles, if desired. As used herein, the term“nanoparticles” refers to particles having an average particle diameterof less than or equal to one micron; for example less than or equal to500 nanometers (nm), or even less than or equal to 150 nm.

Referring again to FIG. 1, the jetted liquid binder precursor material170 is converted (step 190) into a binder material that bonds togetherthe loose powder particles in at least one predetermined region of theloose powder particles to form a layer of bonded powder particles; forexample, by evaporation of a liquid vehicle in the liquid binderprecursor material. In these embodiments, heating the binder material tosufficiently high temperature causes it to volatilize and/or decompose(e.g., “burn out”) during subsequent sintering or infusion steps.

The above steps are then repeated (step 185) with changes to the regionwhere jetting is carried out according to a predetermined designresulting through repetition, layer on layer, in a three-dimensional(3-D) abrasive article preform. In each repetition, the loose powderparticles and the liquid binder precursor material may be independentlyselected; that is, either or both or the loose powder particles and theliquid binder precursor material may be the same as, or different fromthose in adjacent deposited layers.

The abrasive article preform comprises the bonded powder particles andremaining loose powder particles. Once sufficient repetitions have beencarried out to form the abrasive article preform, it is preferablyseparated from substantially all (e.g., at least 85 percent, at least 90percent, preferably at least 95 percent, and more preferably at least 99percent) of the remaining loose powder particles, although this is not arequirement.

If desired, multiple particle reservoirs each containing a differentpowder may be used. Likewise, multiple different liquid binder precursormaterials may be used, either through a common printhead or, preferably,through separate printheads. This results in different powders/bindersdistributed in different and discrete regions of the metal bond abrasivearticle. For example, relatively inexpensive, but lower performingabrasive particles, metal powders, and or binder materials may berelegated to regions of the metal bond abrasive article where it is notparticularly important to have high performance properties (e.g., in theinterior away from the abrading surface). Referring now to FIG. 6, metalbond abrasive wheel 600 has two regions 610, 620. Each region hasabrasive particles 630, 640 retained in a metal bond matrix material650, 660, respectively.

The abrasive article preform is then heated (step 195 in FIG. 1) toremove any organic binder material and/or solvent that may be present,and sinter the metal particles, thereby providing the metal bondabrasive article.

Further details concerning powder bed jetting techniques suitable forpracticing the present disclosure can be found, for example, in U.S.Pat. No. 5,340,656 (Sachs et al.) and U.S. Pat. No. 6,403,002 B1 (vander Geest).

In embodiments in which the loose powder particles include highermelting metal particles and lower melting metal particles, the abrasivearticle preform may be heated sufficiently to cause the lower meltingmetal particles to soften/melt and bond to at least a portion of theloose powder particles, and then cooled to provide the metal bondabrasive article.

In embodiments in which the loose powder particles include highermelting metal particles and no lower melting metal particles, theabrasive article preform may be heated sufficiently to cause the highermelting metal particles to at least sinter and bond to at least aportion of the loose powder particles, and then cooled to provide themetal bond abrasive article.

Cooling may be accomplished by any means known to the art; for examplecold quenching or air cooling to room temperature.

Metal bond abrasive articles and/or abrasive article preforms madeaccording to the present disclosure may comprise a porousmetal-containing matrix (e.g., which may comprise metal particles andabrasive particles, and which may be sintered) with considerableporosity throughout its volume, although this is not a requirement. Forexample, the porous metal-containing matrix may have a void fraction of1 to 60 volume percent, preferably 5 to 50 volume percent, and morepreferably 15 to 50 volume percent, more preferably 40 to 50 volumepercent, although this is not a requirement. Accordingly, the abrasivearticle preform may then be infused with a molten metal that has atemperature below the melting point(s) of any other metallic components,then cooled. Examples of suitable metals that can be made molten andinfused into the abrasive article preform include aluminum, indium,brass, bronze, silver, copper, gold, lead, cobalt, magnesium, nickel,zinc, tin, iron, chromium, silicon alloys, alloys of the foregoing, andcombinations thereof.

Powder bed jetting equipment suitable for practicing the presentdisclosure is commercially available, for example, from ExOne, NorthHuntington, Pa.

Further details concerning sintering and then infusing with molten metalcan be found in, for example, U.S. Pat. No. 2,367,404 (Kott) and U.S.Pat. Appln. Publ. No. 2002/095875 (D'Evelyn et al.).

Metal bond abrasive articles preparable according to methods of thepresent disclosure include essentially any known metal bond abrasivearticle; for example, abrasive pads, grinding bits, abrasive segments,and abrasive wheels. In some preferred embodiments, the metal bondabrasive article comprises at least a portion of a rotary dental tool(e.g., a dental drill bit, a dental bur, or a dental polishing tool). Anexemplary dental bur 200 is shown in FIG. 2. Referring now to FIG. 2,dental bur 200 includes head 230 secured to shank 220. Dental bur 200comprises abrasive particles 205 secured in porous metal bond 210.

During fabrication and testing of such a dental bur (e.g., see Example 3hereinbelow) according to the present disclosure, it was discovered thatreduced swarf buildup during use can be achieved when the bur hassufficient porosity. Although the initial cut rate may be somewhatreduced it is still more than adequate, and the decline in cut rate dueto swarf build up is greatly reduced.

Advantageously, methods according to the present disclosure are suitablefor manufacturing various metal bond abrasive articles that cannot bereadily or easily fabricated by other methods. For example, inclusion ofinternal voids is possible as long as an opening to the exterior of theabrasive preform exists for removal of unbonded loose powder.Accordingly, cooling channels having tortuous and or arcuate paths canbe readily manufactured using methods of the present disclosure. Coolingchannels are open to the exterior of the metal bond abrasive article. Insome embodiments, they have a single opening, but more typically theyhave two or more openings. A cooling medium (e.g., air, water or oil)circulates through the cooling channel(s) to remove heat generatedduring abrading.

Referring now to FIG. 3, exemplary metal bond abrasive wheel 300 hasarcuate and cooling channels 320. Similarly, exemplary metal bondabrasive wheel 400 (shown in FIG. 4) has tortuous cooling channels 420.

FIG. 5 shows an exemplary metal bond abrasive segment 500. In typicaluse, multiple metal bond abrasive segments 500 are mounted evenly spacedalong the circumference of a metal disc to form an abrasive wheel.

Metal bond abrasive wheels can be prepared by sintering correspondinggreen bodies (i.e., having the same general shape features, butcomprising metal bond precursor particles held together by a temporarybinder).

Select Embodiments of the Present Disclosure

In a first embodiment, the present disclosure provides a method ofmaking a metal bond abrasive article, the method comprising thesequential steps:

-   -   a) a subprocess comprising sequentially:        -   i) depositing a layer of loose powder particles in a            confined region, wherein the loose powder particles comprise            higher melting metal particles and abrasive particles, and            wherein the layer of loose powder particles has            substantially uniform thickness;        -   ii) jetting a liquid binder precursor material onto at least            one predetermined region of the layer of loose powder            particles;        -   iii) converting the liquid binder precursor material into a            binder material that bonds together the loose powder            particles in the at least one predetermined region to form a            layer of bonded powder particles;    -   b) independently carrying out step a) a plurality of times to        generate an abrasive article preform comprising the bonded        powder particles and remaining loose powder particles, wherein        the abrasive article preform has a predetermined shape, and        wherein in each step a), the loose powder particles are        independently selected, and the liquid binder precursor material        is independently selected;    -   c) separating substantially all of the remaining loose powder        particles from the abrasive article preform;    -   d) infusing the abrasive article preform with a molten lower        melting metal, wherein at least some of the higher melting metal        particles do not completely melt when contacted by the molten        lower melting metal    -   e) solidifying the molten lower melting metal to provide the        metal bond abrasive article.

In a second embodiment, the present disclosure provides a methodaccording to the first embodiment, wherein the loose powder particlesfurther comprise fluxing agent particles.

In a third embodiment, the present disclosure provides a methodaccording to the first or second embodiment, wherein the abrasiveparticles comprise at least one of diamond particles or cubic boronnitride particles.

In a fourth embodiment, the present disclosure provides a methodaccording to the first or second embodiment, wherein the abrasiveparticles comprise metal oxide ceramic particles.

In a fifth embodiment, the present disclosure provides a methodaccording to any one of the first to fourth embodiments, wherein themetal bond abrasive article includes at least one cooling channel.

In a sixth embodiment, the present disclosure provides a methodaccording to any one of the first to fifth embodiments, wherein themetal bond abrasive article is selected from the group consisting of anabrasive pad, an abrasive grinding bit, abrasive segments, and anabrasive wheel.

In a seventh embodiment, the present disclosure provides a methodaccording to any one of the first to fifth embodiments, wherein themetal bond abrasive article comprises at least a portion of a rotarydental tool.

In an eighth embodiment, the present disclosure provides a methodaccording to the seventh embodiment, wherein the rotary dental tool isselected from the group consisting of dental drills, dental burs, anddental polishing tools.

In a ninth embodiment, the present disclosure provides a methodaccording to any one of the first to eighth embodiments, wherein theliquid binder precursor material comprises a liquid vehicle having apolymer dissolved and/or dispersed therein.

In a tenth embodiment, the present disclosure provides a methodaccording the ninth embodiment, wherein the liquid vehicle predominantlycomprises water.

In an eleventh embodiment, the present disclosure provides a methodaccording to any one of the first to tenth embodiments, wherein thehigher melting metal particles have a melting point that is at least 50degrees Celsius higher than the temperature of the molten lower meltingmetal.

In a twelfth embodiment, the present disclosure provides a method ofmaking a metal bond abrasive article, the method comprising sequentialsteps:

-   -   a) a subprocess comprising sequentially:        -   i) depositing a layer of loose powder particles in a            confined region, wherein the loose powder particles comprise            metal particles and abrasive particles, and wherein the            layer of loose powder particles has substantially uniform            thickness;        -   ii) jetting a liquid binder precursor material onto at least            one predetermined region of the layer of loose powder            particles;        -   iii) converting the liquid binder precursor material into a            binder material that bonds together the loose powder            particles in the at least one predetermined region to form            bonded powder particles;    -   b) independently carrying out step a) a plurality of times to        generate an abrasive article preform comprising the bonded        powder particles and remaining loose powder particles, wherein        the abrasive article preform has a predetermined shape, and        wherein in each step a), the loose powder particles are        independently selected, and the liquid binder precursor material        is independently selected;    -   c) separating substantially all of the remaining loose powder        particles from the abrasive article preform; and    -   d) heating the abrasive article preform to provide the metal        bond abrasive article.

In a thirteenth embodiment, the present disclosure provides a methodaccording to the twelfth embodiment, wherein the loose powder particlesfurther comprise fluxing agent particles

In a fourteenth embodiment, the present disclosure provides a methodaccording to the twelfth or thirteenth embodiment, wherein the abrasiveparticles comprise at least one of diamond particles or cubic boronnitride particles.

In a fifteenth embodiment, the present disclosure provides a methodaccording to the twelfth or thirteenth embodiment, wherein the abrasiveparticles comprise metal oxide ceramic particles.

In a sixteenth embodiment, the present disclosure provides a methodaccording to any one of the twelfth to fifteenth embodiments, whereinthe metal particles comprise a combination of higher melting metalparticles and lower melting metal particles, wherein the higher meltingmetal particles have a melting point that is at least 50 degrees Celsiushigher than the temperature of the molten lower temperature metal.

In a seventeenth embodiment, the present disclosure provides a methodaccording to any one of the twelfth to sixteenth embodiments, whereinthe metal bond abrasive article includes at least one cooling channel.

In an eighteenth embodiment, the present disclosure provides a methodaccording to any one of the twelfth to seventeenth embodiments, whereinthe metal bond abrasive article is selected from the group consisting ofan abrasive pad, an abrasive grinding bit, abrasive segments, and anabrasive wheel.

In a nineteenth embodiment, the present disclosure provides a methodaccording to any one of the twelfth to seventeenth embodiments, whereinthe metal bond abrasive article comprises at least a portion of a rotarydental tool.

In a twentieth embodiment, the present disclosure provides a methodaccording to the nineteenth embodiment, wherein the rotary dental toolis selected from the group consisting of dental drills, dental burs, anddental polishing tools.

In a twenty-first embodiment, the present disclosure provides a methodaccording to any one of the twelfth to twentieth embodiments, whereinthe liquid binder precursor material comprises a liquid vehicle having apolymer dissolved and/or dispersed therein.

In a twenty-second embodiment, the present disclosure provides a methodaccording to the twenty-first embodiment, wherein the liquid vehiclepredominantly comprises water.

In a twenty-third embodiment, the present disclosure provides a metalbond abrasive article comprising a metallic binder material havingabrasive particles retained therein, wherein the metal bond abrasivearticle has at least one tortuous cooling channel extending at leastpartially therethrough.

In a twenty-fourth embodiment, the present disclosure provides a metalbond abrasive article comprising a metallic binder material havingabrasive particles retained therein, wherein the metal bond abrasivearticle has at least one arcuate cooling channel extending at leastpartially therethrough.

In a twenty-fifth embodiment, the present disclosure provides a metalbond abrasive article according to any one of the twenty-third totwenty-fourth embodiments, wherein the abrasive particles comprise firstabrasive particles and second abrasive particles, wherein the firstabrasive particles and second abrasive particles are disposed ininterspersed predetermined different regions within the metal bondabrasive article.

In a twenty-sixth embodiment, the present disclosure provides a metalbond abrasive article according to the twenty-fifth embodiment, whereinthe different regions are layers.

In a twenty-seventh embodiment, the present disclosure provides a metalbond abrasive article according to any one of the twenty-third totwenty-sixth embodiments, wherein the abrasive particles comprise atleast one of diamond particles or cubic boron nitride particles.

In a twenty-eighth embodiment, the present disclosure provides a metalbond abrasive article according to any one of the twenty-third totwenty-seventh embodiment, wherein the abrasive particles comprise metaloxide ceramic particles.

In a twenty-ninth embodiment, the present disclosure provides a metalbond abrasive article according to any one of the twenty-third totwenty-eighth embodiments, wherein the metal bond abrasive article isselected from the group consisting of an abrasive pad, an abrasivegrinding bit, abrasive segments, and an abrasive wheel.

In a thirtieth embodiment, the present disclosure provides a metal bondabrasive article according to any one of the twenty-third totwenty-ninth embodiments, wherein the metal bond abrasive articlecomprises a porous metal-containing matrix having a void fraction of 15to 50 volume percent.

In a thirty-first embodiment, the present disclosure provides a metalbond abrasive article according to any one of the twenty-third tothirtieth embodiments, wherein the metal bond abrasive article comprisesat least a portion of a dental tool.

In a thirty-second embodiment, the present disclosure provides a metalbond abrasive article according to the thirty-first embodiment, whereinthe dental tool is selected from the group consisting of dental drills,dental burs, and dental polishing tools.

In a thirty-third embodiment, the present disclosure provides a metalbond abrasive article precursor comprising metallic particles andabrasive particles bonded together by a binder precursor material,wherein the metal bond abrasive article precursor further comprises atleast one of:

-   -   at least one tortuous cooling channel extending at least        partially through the metal bond abrasive article precursor; or    -   at least one arcuate cooling channel extending at least        partially through the metal bond abrasive article precursor.

In a thirty-fourth embodiment, the present disclosure provides a rotarydental tool, wherein at least a portion of the dental tool comprisesabrasive particles dispersed and retained in a porous metal bond matrixcomprising sintered metal particles.

In a thirty-fifth embodiment, the present disclosure provides a rotarydental tool according to the thirty-fourth embodiment, wherein thedental tool is a dental bur.

In a thirty-sixth embodiment, the present disclosure provides a rotarydental tool according to the thirty-fourth or thirty-fifth embodiment,wherein the rotary dental tool comprises a porous metal-containingmatrix having a void fraction of 15 to 50 volume percent.

Objects and advantages of this disclosure are further illustrated by thefollowing non-limiting examples, but the particular materials andamounts thereof recited in these examples, as well as other conditionsand details, should not be construed to unduly limit this disclosure.

EXAMPLES

Unless otherwise noted, all parts, percentages, ratios, etc. in theExamples and the rest of the specification are by weight. In theExamples: ° C.=degrees Celsius, g=grams, min=minute, mm=millimeter,sec=second, and rpm=revolutions per minute.

Table 1, below, lists abbreviations for materials used in the Examples.

TABLE 1 ABBRE- VIATION DESCRIPTION PDR1 PM-R1-S4-30 stainless steelpowder from The ExOne Company, North Huntingdon, Pennsylvania PDR2 CMD,200/230 Mesh, D76 diamond powder from Pinnacle Abrasives, Santa Rosa,California PDR3 LS00 270/325 diamond powder from Lands SuperabrasivesCo., New York, New York PDR4 DURALUM SPECIAL WHITE 60 grit aluminumoxide powder from Washington Mills Electro Minerals, Niagara Falls, NewYork BIN Ether solvent-based polymer binder, obtained as PM-B-SR1-04from The ExOne Company, North Huntingdon, Pennsylvania BRO1 PM-I-R1bronze powder from The ExOne Company, North Huntingdon, PennsylvaniaBRO2 LS431155LO/Cu226020/1 bronze powder (Cu80/Sn20, maximum particlesize 53 micron) from Goodfellow Cambridge Limited, Huntington, EnglandBRO3 FINE SPHERICAL BRONZE POWDER - GRADE 80/20 bronze powder(Cu80/Sn20) with max particle size 53 micron, from Foxmet S.A.,Dondelange, Luxembourg

Example 1

A print material (400 g) was prepared by mixing, based on the mixtureweight, 89% of PDR1, and 11% of PDR2. The print material was filled intothe build box of an X1-Lab 3D printer obtained from The ExOne Company,North Huntingdon, Pa. The binder supply bottle of the printer was filledwith BIN. 3D printing was executed using printing protocol andprocedures according to the manufacturer's operating instructions usingthe following operation parameters for stainless steel: layer height=100microns, spreader speed=25 mm/sec, printing saturation=70% level, anddrying time=60 sec at 90% heater power. During the printing process, thepowder mixture spread well and formed uniform, flat layers. The diamondgrains looked evenly distributed. After printing finished, the powderbed, including the object and surrounding powder was removed from theprinter, and placed into an ambient atmosphere oven to cure for 2 hoursat 195° C. The printed and hardened object was removed from the powderbed and loose powder was removed using a soft bristle brush.

The segment object was then infiltrated with bronze as follows. Theobject was placed onto capillary stems in a 3D-printed cup, made of PDR1and made according to the manufacturer's guidelines, filled with BRO1.This cup, including the object and infiltrant BRO1, was placed in afurnace and heated with the following protocol: vacuum was applied inthe furnace for 10 min at 23° C., after which the furnace was filledwith nitrogen and the temperature was ramped at 10° C./min to 250° C.and held for 10 min, then ramped at 10° C./min to 420° C. and held for30 min, after that, the temperature was ramped at 10° C./min to 630° C.and held for 90 min, then ramped at 5° C./min to 1100° C. and held for 1min, then ramped at 2° C./min to 1125° C. and held for 90 min. In thisprocess, the binder was burned out, and the bronze melted and movedthrough the capillary stems to infiltrate the printed segment object.The furnace was then cooled down to 23° C. at 10° C./min. Afterreturning to room temperature, the cup with the attached infiltratedobject was removed from the furnace, and the object was removed from thestems.

The resulting abrasive segment is shown in FIG. 5 and had the dimensionsof 2.5 cm length×2.5 cm width of the outer (largest) surface and 0.6 cmthickness. The abrasive segment was tested for abrasive function asfollows. The object was fixed in a vise. A rotating steel milling cutterwas urged against the abrasive segment. The development of smoke andgeneration of heat was readily observed when the milling cutter andabrasive segment came into contact. Visual inspection revealed that thecutting edge and flutes of the steel tool were heavily abraded as aresult of the contact with the infiltrated abrasive segment.

Example 2

A print material (400 g) was prepared by mixing, based on the mixtureweight, 70% of PDR1, 11% of PDR2, and 19% of BRO2. The print materialwas filled into the build box of an X1-Lab 3D printer obtained from TheExOne Company. The binder supply bottle of the printer was filled withBIN. 3D printing was executed using printing protocol and proceduresaccording to the manufacturer's operating instructions using thefollowing operation parameters for stainless steel: layer height=100microns, spreader speed=5 mm/sec, printing saturation=100% level, anddrying time=60 sec at 90% heater power. After the printing finished, thepowder bed, including the object and surrounding powder was removed fromthe printer, and placed into an ambient atmosphere oven to cure for 2hours at 195° C. After cooling to 23° C., the printed and hardened diskwas then extracted from the powder bed and loose powder was removedusing a soft bristle brush. The resulting abrasive article was a flatdiamond cutting disc with a 22 mm outer diameter, a 1.5 mm diametercenter hole and a 0.6 mm thickness.

The disk was placed within a bed of PDR4 in a graphite crucible. Thecrucible was then placed in a furnace and heated under a nitrogenatmosphere with the heating protocol as described in Example 1. Aftercooling to 23° C., it was observed that the bronze had melted and boundthe stainless steel and diamond grain to form a porous but stable part.The part had shrunk by approximately 3% as measured by comparing thediameter of the disk before and after heating using a digital caliper.

Example 3

A print material (400 g) was prepared by mixing, based on the mixtureweight, 45% of PDR1, 25% of PDR3, and 30% of BRO2. The print materialwas filled into the build box of an X1-Lab 3D printer obtained from TheExOne Company. The binder supply bottle of the printer was filled withBIN. 3D printing was executed using printing protocol and procedures toprint a dental bur head precursor part in the shape of dental bur head210 in FIG. 2 (outer diameter=5 mm, inner diameter=3 mm) according tothe manufacturer's operating instructions using the following operationparameters for stainless steel: layer height=200 microns, spreaderspeed=5 mm/sec, printing saturation=120% level, and drying time=120 secat 90% heater power. The powder mixture spread well and formed uniform,flat layers. The diamond grains looked evenly distributed. After theprint process finished, the powder bed, including the object andsurrounding powder was removed from the printer, and placed into anambient atmosphere oven to cure for 2 hours at 195° C. After cooling to23° C., the printed and hardened dental bur head precursor was thenextracted from the powder bed and loose powder was removed using a softbristle brush.

A 3 mm diameter×40 mm length, stainless steel shank was inserted intothe dental bur head. The resulting assembly was immersed in PDR4 andplaced in a furnace and heated under a nitrogen atmosphere with theprotocol below: vacuum was applied in a furnace for 10 min at 23° C.,after which the furnace was filled with nitrogen. Then the vacuum wasapplied again for 10 min at 23° C., and the furnace was filled withnitrogen and temperature was ramped at 5° C./min to 500° C. and held for60 min, then ramped at 2° C./min to 600° C. and held for 90 min, afterthat, the temperature was ramped at 2.5° C./min to 1000° C. and held for1 min, then ramped at 2° C./min to 1120° C. and held for 90 min. Thefurnace then was allowed to cool down to 23° C. and the resultant dentalbur shown in FIG. 2 was removed (dental bur head: outer diameter=5 mm,inner diameter=3 mm). Following heat treatment, the head was fullyadhered to the shank. The porosity of the dental bur head was measuredusing a pycnometer (ACCUPYC 1330 from Micrometrics Corporation,Norcross, Ga.) and found to be 43%.

Abrading Test

The dental bur of Example 3 was inserted into a Dremel drill which wasin a test fixture that allowed to push the bur against a test coupon ata controlled force. The test coupon was a block of Filtek Supreme UltraUniversal dental restorative composite material, (3M ESPE, Saint Paul,Minn.), which was cast into a block 15 by 25 by 1.8 mm in size, andlight cured for 20 seconds exposure of each of the 2 major surfaces,using a UV-Vis LED Source model CF2000 (Clearstone Tech, Hopkins, Minn.)set at 84 power. A thermocouple was attached to one major surface of thetest coupon. The drill was set to a rotational speed of 10000 RPM andthe force was set to 200 gf. The bur was moved against the major surfaceof the coupon opposite the thermocouple for 60 seconds and thetemperature rise was recorded after 0, 30, 45 and 60 seconds,respectively. It was observed that the bur removed material and createda notch. The bur was removed and viewed at 100× magnification usingscanning electron microscopy (SEM). It was observed that there was noswarf buildup on the bur.

The procedure was repeated using a comparative commercially availabledental bur (model 840 11 055 MED FLTE Cylin, 100 micron diamond, fromBrasseler USA, Savannah, Ga.) having the same outer diameter. ComparingSEM images of this comparative bur before and after the abrading, it wasobserved that there was significant visible swarf buildup on thecomparative bur (model 840 11 055 MED FLTE Cylin).

Table 2 shows a temperature during abrading for the dental burs ofExample 3 and the comparative bur (model 840 11 055 MED FLTE Cylin) inthe above procedure. Reduced heating correlates with reduced thermaldamage to a living tooth during abrading.

TABLE 2 TEMPERATURE, ° C. DURATION OF DENTAL COMPARATIVE DENTALABRADING, BUR OF BUR, model 840 11 055 seconds EXAMPLE 3 MED FLTE Cylin0 25.0 25.0 30 37.0 37.0 45 40.0 42.0 60 42.5 46.0

All cited references, patents, and patent applications in the aboveapplication for letters patent are herein incorporated by reference intheir entirety in a consistent manner. In the event of inconsistenciesor contradictions between portions of the incorporated references andthis application, the information in the preceding description shallcontrol. The preceding description, given in order to enable one ofordinary skill in the art to practice the claimed disclosure, is not tobe construed as limiting the scope of the disclosure, which is definedby the claims and all equivalents thereto.

What is claimed is:
 1. A method of making a metal bond abrasive article,the method comprising the sequential steps: a) a subprocess comprisingsequentially: i) depositing a layer of loose powder particles in aconfined region, wherein the loose powder particles comprise highermelting metal particles and abrasive particles, and wherein the layer ofloose powder particles has substantially uniform thickness; ii) jettinga liquid binder precursor material onto at least one predeterminedregion of the layer of loose powder particles; iii) converting theliquid binder precursor material into a binder material that bondstogether the loose powder particles in the at least one predeterminedregion to form a layer of bonded powder particles; b) independentlycarrying out step a) a plurality of times to generate an abrasivearticle preform comprising the bonded powder particles and remainingloose powder particles, wherein the abrasive article preform has apredetermined shape, and wherein in each step a), the loose powderparticles are independently selected, and the liquid binder precursormaterial is independently selected; c) separating substantially all ofthe remaining loose powder particles from the abrasive article preform;d) infusing the abrasive article preform with a molten lower meltingmetal, wherein at least some of the higher melting metal particles donot completely melt when contacted by the molten lower melting metal;and e) solidifying the molten lower melting metal to provide the metalbond abrasive article.
 2. The method of claim 1, wherein the loosepowder particles further comprise fluxing agent particles.
 3. The methodof claim 1, wherein the abrasive particles comprise at least one ofdiamond particles or cubic boron nitride particles.
 4. The method ofclaim 1, wherein the abrasive particles comprise metal oxide ceramicparticles.
 5. The method of claim 1, wherein the metal bond abrasivearticle includes at least one cooling channel.
 6. The method of claim 1,wherein the metal bond abrasive article is selected from the groupconsisting of an abrasive pad, an abrasive grinding bit, abrasivesegments, and an abrasive wheel.
 7. The method of claim 1, wherein themetal bond abrasive article comprises at least a portion of a rotarydental tool.
 8. The method of claim 1, wherein the liquid binderprecursor material comprises a liquid vehicle having a polymer dissolvedtherein.
 9. The method of claim 8, wherein the liquid vehiclepredominantly comprises water.
 10. The method of claim 1, wherein thehigher melting metal particles have a melting point that is at least 50degrees Celsius higher than the temperature of the molten lower meltingmetal.
 11. The method of claim 1, further comprising, between steps c)and d), burning off at least a portion of the binder material.
 12. Amethod of making a metal bond abrasive article, the method comprisingsequential steps: a) a subprocess comprising sequentially: i) depositinga layer of loose powder particles in a confined region, wherein theloose powder particles comprise metal particles and abrasive particles,and wherein the layer of loose powder particles has substantiallyuniform thickness; ii) jetting a liquid binder precursor material ontoat least one predetermined region of the layer of loose powderparticles; iii) converting the liquid binder precursor material into abinder material that bonds together the loose powder particles in the atleast one predetermined region to form bonded powder particles; b)independently carrying out step a) a plurality of times to generate anabrasive article preform comprising the bonded powder particles andremaining loose powder particles, wherein the abrasive article preformhas a predetermined shape, and wherein in each step a), the loose powderparticles are independently selected, and the liquid binder precursormaterial is independently selected; c) separating substantially all ofthe remaining loose powder particles from the abrasive article preform;and d) heating the abrasive article preform to provide the metal bondabrasive article.
 13. The method of claim 12, wherein the loose powderparticles further comprise fluxing agent particles.
 14. The method ofclaim 12, wherein the abrasive particles comprise at least one ofdiamond particles or cubic boron nitride particles.
 15. The method ofclaim 12, wherein the abrasive particles comprise metal oxide ceramicparticles.
 16. The method of claim 12, wherein the metal particlescomprise a combination of higher melting metal particles and lowermelting metal particles, wherein the higher melting metal particles havea melting point that is at least 50 degrees Celsius higher than thetemperature of the molten lower temperature metal.
 17. The method ofclaim 12, wherein the metal bond abrasive article includes at least onecooling channel.
 18. The method of claim 12, wherein the metal bondabrasive article is selected from the group consisting of an abrasivepad, an abrasive grinding bit, abrasive segments, and an abrasive wheel.19. The method of claim 12, wherein the metal bond abrasive articlecomprises at least a portion of a rotary dental tool.
 20. The method ofclaim 12, wherein the liquid binder precursor material comprises aliquid vehicle having a polymer dissolved therein.
 21. The method ofclaim 20, wherein the liquid vehicle predominantly comprises water.